Radić’s 40m span tensile roof does its level best to minimise its impact on the landscape. · Credit: Cristobal Palma

Wineries have latterly become enthusiastic clients of the world’s leading architects, with Foster’s, Rogers Stirk Harbour, Santiago Calatrava and Jean Nouvel to name but a few turning their hands to this most niche of sectors.

The latest addition to this catalogue is the VIK Winery, designed at Millahue in the foothills of the Chilean Andes by Smiljan Radić, best known in the UK as the architect of the boulder-like Serpentine Pavilion in 2014.

Not for him the showy mirrored red panels of Nouvel’s Château La Dominique or the energetically undulating aluminium roof of Calatrava’s Bodegas Ysios in the Rioja region. Instead, Radić used a 10,600m2 PTFE fibreglass roof to create a lightweight and unassuming intervention in the landscape that does its best not to be noticed.

His inspiration for the 40m-span roof was the traditional use of fabrics stretched out in the vineyards to shade those harvesting the grapes. Radić embedded the building in the landscape for minimal impact and stretched a tensile roof between two reinforced concrete walls cast in situ. From afar, the white roof appears to float in the fields. This feeling of lightness was a primary objective, and can also be felt in the interior, according to the architect.

‘With our projects we always try to do the least possible damage to the surroundings,’ he says. ‘The winery was buried throughout its length to avoid stealing the limelight from the landscape.’

As a result, the vineyard itself – not the winery – remains the landscape’s main character according to VIK, which was established by Norwegian entrepreneur Alexander Vik.

By submerging the 16,000m2 building, the firm also avoided the need to install air-conditioning in most of its spaces, instead using a natural free-cooling system.

Radić was keen that the design of the building should show the manufacturing process rather than conceal it. The roof spans a vast vat hall of stainless steel fermentation tanks and overhead walkways. A tensile design formed by a double membrane of PTFE was the ­commonsense choice – both practically and conceptually – says Radić. He had previously considered using a pneumatically, pre-stressed roof structure with PVC but this proved too
expensive, so instead specified a standard steel structure with two layers of PTFE membrane.

‘The membranes are a simple high-tech material and very easy to use when you choose the right project, although – oddly – many people do not consider them as permanent structures, but simply as something ephemeral. This reading is very important for me because it allows the building to be seen as something more tender, less invasive,’ says Radić.

Among other important factors were the membrane’s lightness and the ability of the translucent PTFE fabric to allow in sufficient but not too much natural light throughout the day, thus reducing energy requirements. This half-light is apparently an optimal condition for winemaking. At the same time, the outer membrane’s 73% heat and light reflectance (compared with 8% for clear glass) allows the winery to avoid excessive overheating.

Specification of the two layers is different in relation to warp and fill reinforcement, lower breakage strength and trapezoidal tear resistance. As well as its 12% solar transmission performance, the upper layer’s key function is water­proofing, while the lighter inner skin plays a significant acoustic role.

‘It was important to maintain the optimal acoustic levels in a room that holds many people at harvest time,’ says Radić.

The roof is cantilevered over glass walls at both ends to form shading canopies – important since the building is oriented east/west. At the entrance, it looks onto a Japanese-inspired garden forecourt of boulders and water, the latter helping to cool the barrel room below. At the rear, the cantilever faces a small wine-tasting pavilion, also designed by Radić, where visitors, having perused the vats, can finally enjoy the contents.

The success of the membrane roof on the VIK winery has led Radić to use a tensile roof on another project – a theatre in the south of Chile.

The PTFE roof was achieved through a collaboration with Birdair, the American specialist tensile membrane contractor which designed and executed the structural steel and membrane roofing system. The roof structure comprises 11 lenticular steel trusses interconnected with circular hollow sections and supported on reinforced concrete walls. These trusses were produced in China for Birdair before being transported to Chile and assembled on site, with the trusses fixed to steel bearings at the top of the concrete walls. The inner and outer PTFE skins span the space between the top and bottom members of the trusses.

In the installation, rolls of the Sheerfill II outer membrane were tensioned over the top of the steel trusses. The corresponding inner PTFE lining was hoisted into place beneath using steel cables fixed at the eaves. All joints between the sheets are PTFE, sealed using specialist, highly heated irons in combination with heat-sensitive tape. These form durable, permanent joints. Extruded aluminium clamping attached to the steel roof structure is then used to connect and clamp the membrane panels.

As well as providing the desired acoustic performance, the inner layer of the Fabrasorb I absorptive membrane conceals the trusses and their associated steelwork.